1. Technical Field
The present invention relates to a method of fabricating a semiconductor device, and more particularly to a method of fabricating an image sensor and a method of reworking an image sensor.
2. Description of the Related Art
Generally, optoelectronic devices that may convert light into electronic signals include CMOS image sensors (CISs) and charge coupled devices (CCDs).
Because the CMOS image sensors can be used in a low voltage condition and fabricated by a CMOS process, production cost and size of the CMOS image sensors can be reduced dramatically. And thus, the CMOS image sensors have replaced the charge coupled devices to be used in digital electronics gradually.
FIG. 1 is a schematic, side cross-sectional view of a conventional CMOS image sensor.
Please referring to FIG. 1, the CMOS image sensor includes a substrate 100 having a pixel array region 101 and a pad region 103. A plurality of shallow trench isolation structures 102 and a plurality of photodiodes (not shown) formed at the photo sensitive cells 104 in the substrate 100. The shallow trench isolation structures 102 surround the photo sensitive cells 104. The CMOS transistors disposed on a surface of the substrate 100 (not shown) are electrically connected with the photo sensitive cells 104. The shallow trench isolation structures 102 are used to avoid short circuit between the photo sensitive cells 104 and the other elements.
In addition, a metal interconnect structure and a plurality of inter-layer dielectric layers 106 is disposed on the substrate 100, so as to cover the photo sensitive cells 104 and the shallow trench isolation structures 102. A plurality of patterned metal layers 108, 110 are disposed on the metal interconnect structure and a plurality of inter-layer dielectric layers 106. The patterned metal layers 110 are used as bonding pads. Another planarized layer 112 is also disposed on the substrate 100, so as to cover the patterned metal layers 108, 110. The planarized layer 112 has an opening 114 to expose the patterned metal layer 110.
A color filter array 116 is disposed corresponding to the photo sensitive cells 104 above the pixel array region 101. The color filter array 116 is made of a red filtering pattern, a green filtering pattern and a blue filtering pattern. In addition, a planarized layer 118 is disposed on the color filter array 116, and a plurality of microlenses 120 are disposed in the planarized layer 118.
In addition, a capping layer 130 that is made of an oxide layer is further formed on the microlenses 120. The capping layer 130 is used to protect surfaces of the microlenses 120.
However, the capping layer 130 can not be removed completely and easily. As such, if some defects about the color filter array 116 or the microlenses 120 are observed, before the CMOS image sensor is fabricated or when the conventional CMOS image sensor is carried out a performance testing, the color filter array 116 or the microlenses 120 would not be reworked. Consequently, some problems, such as, rejecting the whole CMOS image sensor, low product yield and high product cost, would be generated.
What is needed, therefore, is a new method of fabricating an image sensor and a new method of reworking an image sensor that can overcome the above-mentioned shortcomings.